Method for dyeing textile materials



United States Patent 3,124,411 METHOD FOR DYEING TEXTILE MATERIALS WITH VAT DYES Gilbert S. Panson and Carol E. Weill, Livingston, NJ., assignors to Metal Hydrides Incorporated, Beverly, Mass., a corporation of Massachusetts No Drawing. Filed July 17, 1961, Ser. No. 124,373

6 Claims. (Cl. 834) This invention relates to dyeing textile materials with vat dyes.

Textile materials, such as cotton fabrics, usually are dyed by padding a vat dye on to the fabric, squeezing out the excess, and then passing the dye impregnated fabric through an aqueous bath containing sodium hydroxide, sodium hydrosulfite and sodium chloride. The reducing liquor reduces the dye and converts it to the water soluble sodium leuco form, the presence of the salt shifting the equilibrium of the reduced dye from the solution to the fabric. The cloth then is removed from the bath and the dye oxidized to give a level dyeing of desired shade. This procedure requires the use of as much as to 40 fold excess of hydrosulfite over the stoichiometric requirement since the hydrosulfite is very unstable under the conditions of air oxidation present in dyeing and the high temperatures used in the dyeing operation.

It has been proposed heretofore that an alkali metal bisulfite, such as sodium bisulfite, can be converted to alkali metal hydrosulfite in an aqueous medium by the addition of an alkali metal borohydride, such as sodium or potassium borohydride. Thereafter, an alkali metal hydroxide may be added and the resulting alkaline solution may be used for reducing vat dyes and for dyeing textile fabrics by immersing the textile fabric in the alkaline hydrosulfite solution. This procedure does not solve the instability problem of the hydrosulfite and requires the substantial absence of alkaline metal hydroxide during the reaction between the alkali metal bisulfite and alkali metal borohydride.

The present invention is based upon the discovery that if a textile fabric is impregnated with a mixture of a vat dye and an alkali metal bisulfite and the thus impregnated fabric is passed through a reducing liquor con sisting of an aqueous solution of an alkali metal hydroxide and an alkali metal borohydride having a pH between about 9.5 and 13, the vat dye is reduced and converted to its water soluble alkali leuco form. Thus, in accordance with the method of the present invention, a mixture of a vat dye and an alkali metal bisulfite, such as sodium bisulfite, in the form of an aqueous dispersion is padded on to the textile fabric, the excess being squeezed out. The thus impregnated fabric then is passed through an aqueous reducing solution consisting essentially of an alkali metal hydroxide, such as sodium hydroxide, an alkali metal borohydride, such as sodium or potassium borohydride, and a salt, such as sodium chloride. The fabric then is removed from the reducing solution and subjected to an oxidizing operation.

Since the composition of the various vat dyes varies, the amounts of alkali metal bisulfite and alkali metal borohydride required in the practice of the invention will vary. In general, about 4 to 400 parts by weight of alkali metal bisulfite and about 0.2 to 20 parts by weight of alkali metal borohydride per 100 parts by weight of vat dye may be used. The use of greater amounts of bisulfite and borohydride are not harmful. It will be understood that in a continuous dyeing operation, the concentration of alkali metal hydroxide, alkali metal borohydride, and salt in the reducing bath must be maintained sufficiently high and, preferably, substantially constant to effect the desired reduction and obtain level dye- The amount of sodium hydroxide required in the reducing bath varies with the class of vat dye used and can be determined from the booklets published by the dye manufacturer. Each dye works best at a certain sodium hydroxide level. Sufiicient sodium hydroxide in excess of the amount required to convert the dye to its alkali leuco form must be present to stabilize the bath.

In some instances in commercial operation it is desirable to dry the impregnated fabric before immersion in the reducing bath. Cloth impregnated with vat dye and sodium bisulfite in accordance with the invention can be dried at 110 C. for 1 to 2 hours and then immersed in the reducing bath and obtain the desired shade. This indicates the great stability of the mixture of bisulfite and vat dye.

Reduction of the dye to the sodium leuco and exhaustion of the dye in to the fabric is dependent upon the temperature of the bath and the time of contact. At high temperatures, such as C. and higher, the contact time is less than 10 seconds which makes the invention particularly useful for continuous dyeing, such as in the Williams unit. At lower temperatures, longer contact times are needed to insure full reduction and penetration of the dye. The latter conditions are more useful in the Beck dyeing operations or package dyeing operations where longer contact times are needed.

The mixture of alkali metal bisulfite and vat dye used in the practice of the invention is completely stable and can be stored for long periods of time. The aqueous solution of alkali metal hydroxide and alkali metal borohydride is available in concentrations which also are extremely stable even at high temperatures for long periods of time. When the fabric impregnated with the mixture of alkali metal bisulfite and vat dye is passed into the reducing solution, the vat dye is reduced and converted to its water soluble alkali leuco form in a vey few seconds. Consequently, the residence time required in the reducing bath is very short and there is very little opportunity for the side reaction of air oxidation to occur. This is of particular industrial significance because it makes possible vatting operations with substantially less reducing agent than has heretofore been required.

While we have described the use of the alkali metal borohydrides in thepractice of the invention, the quaternary ammonium borohydrides may be used in place thereof if desired. As illustrative of water soluble quaternary ammonium borohydrides we may mention the lower tetraalkyl ammonium borohydrides, such as tetramethyl, tetraethyl, trimethyl ethyl, dimethyl diethyl ammonium borohydrides, as well as quaternary ammonium borohydrides responding to the formula R (CH NBH where R is a saturated or unsaturated straight chain aliphatic hydrocarbon radical containing about 7 to 21 carbon atoms, x and y are integers from 1 to 3, and x plus y equals 4, such as tricapryl methyl ammonium borohydride, cetyl trimethyl ammonium borohydride, etc.

We have successfully used in the practice of the invention many vat dyes selected from the various types commonly used in commercial practice. As illustrative of such vat dyes we may mention anthraquinone type dyes, such as Mayvat Jade Green (C.I. #59,105), Carbanthrene Blue BCS (C.I. #69,825), Ponsul Brilliant Violet 4RN (C.I. #60,0l0), Ponsul Golden Orange 3G (C.I. #69,025), Indanthrene Golden Yellow RK (Vat Orange 1, Cl. #59,l05/6), Indanthrene Brilliant Orange RK (Vat Orange 3, Cl. #59,300), Amanthrene Golden Orange F (Vat Orange 9, Cl. #59,700), Indanthrene Orange RRT (Vat Orange 1, Cl. #59,705), and Indanthrene Dark Blue BO (Vat Blue 20, Cl. #59,800), Tinon Navy Blue RAF (Vat Blue 18, CL #59,815), Ahcovat Jade Green B (Vat Green 1, Cl. #59,825), Indanthrene Brilliant Violet 3B (Vat Violet 9, Cl.

#60,005), Cibanone Violet 4R (Vat Violet 1, CI. 60,010); anthraquinone type dyes containing amino groups, such as Cibanone Black DRB (Vat Black 9, Cl. #155,230); dyes containing a heterocyclic nucleus fixed to a central vatting system, such as Indanthrene Red FBB (Vat Red 10, 01. #67,000), Tinon Yellow (Vat Yellow 2, 0.1. #67300), Carbanthrene Red BN (Vat Red 35, Cl. #613,000), Cibanone Violet BNA (Vat Violet 13, 01. #68,700), Indanthrene Brown RN (Vat Brown 3, 01. #69,015), Indanthrene Red Brown RF (Vat Brown 25, 0.1. 69,020), Tinon Olive BF (Vat Green 3, CI. #69500), Tinon Olive SF (Vat Black 25, CI. #69525), Cibanone Blue GCDN (Vat Blue 14, Cl. 68,810), Ponsul Blue BF (Vat Blue 6, 0.1. #69,825), Indanthrene Khaki GG (Vat Green 8, 0.1. #71,050); indigo and its derivatives and homologues, such as Cibanone Blue 2BGD (Vat Blue 5, 0.1. #73,065); thioindigo and its derivatives and homologues, such as Hostavat Brilliant Pink R (Vat Red 1, 01. $173,360), Indanthrene Printing Violet 6R (Vat Violet 3, CI. #73395); phthalocyanine dyes, such as Algol Brilliant Blue 40 (Vat Blue 29, 0.1. #174,140).

The invention is illustrated further by the following specific examples, the results of which are shown in the following tables. In all of these examples level dyeings to the shade specified by the dye manufacturer were obtained. In these tables the term reduced indicates proper sodium leuco was formed and samples of cloth dyed gave the color and shade indicated by the dye manufacturer.

In the following tables the following formulations were used as standard unless otherwise indicated in the table.

PAD BATH 4.0 grams of vat dye (as a single paste) was diluted with 125.0 grams of water and 8.3 grams of sodium bisulfite was stirred into the diluted paste. Variable amounts of water or dye can be used depending upon the final shade desired. Cotton cloth was immersed in this mixture and then passed through squeeze rolls to remove the excess.

REDUCING BATH The standard reducing bath contained 0.2 gram of sodium hydroxide, 0.4 gram of sodium borohydride, 20 grams of sodium chloride and 250 grams of water. The bath was heated to 80 C. The cloth from the squeeze rolls was passed into the reducing bath where reduction took place rapidly. The cloth then was removed and subjected to a conventional oxidizing operation.

Table I Example Dye Used Temp. pH Contact Comment 0.) Time 1 Vat Red 1, (0.1. 80 11.3 5 see Re- #73, duced. 2 Vat Red 29, (0.1. 80 11.3 5see Do.

1, 3 Vat Orange 5, (0.1. 80 11.3 5 seo Do.

#73,33 4" Vat Yellow 2, (0.I. 80 11.3 5sec Do.

5 Vat Y e1ibw 4, 0.1. 80 11.3 5sec Do.

#59,1 6 Vat Green 1, (0.1. 24 11.45 5min Partially 9,8 reduced. 7 do 80 11.8 5see Reduced. 8... do Boil 11.25 1sec Do. 9 Vat3Blue5, (0.1. 80 11.3 55%.... Do.

#7 10 Vat Blue 6, (0.1. 80 11.3 1sec Do.

#69, 11 Vat Blue 20, 0.1. so 11.3 5sec Do. #5

12 Vat Blue 43, (0.I. 80 11.3 5see Do.

13 Vat zjl'aiolet a, 0.1. 30 11.3 5sec D0.

96 14 Vat Black 25, 0.1. 80 11.3 55%-"- Do 4% The pH indicated is that at the temperature shown in the table before immersing the impregnated cloth.

Table II This table illustrates the effect of the ratio of dye to sodium bisulfite, the dye used being Vat Green 1 (0.1. 73,360).

Dye in NaHSOa Ratio of Example grams in grams dye to pH Comment NaHSOa 15.0 0.5 30.0 11.3 Reduction incomplete 20.0 1.0 20.0 11.3 Reduced 10.0 1.0 10.0 11.3 Do. 15.0 8.3 1.8 11.3 Do. 4.0 8.3 0.48 11.3 Do. 4.0 12.0 0.33 11.3 D0.

The pH is that at the temperature of C. before immersing the impregnated cloth.

Table III This table illustrates the effect of the ratio of sodium bisulfite to sodium borohydride, the dye used being Vat The pH indicated is that at a temperature of 80 C. before immersing the impregnated cloth.

We claim:

1. In a method for continuously dyeing textile materials with vat dyes which involves padding the textile material with an aqueous dispersion of the vat dye and passing the dye impregnated textile material through an aqueous solution of a vat dye reducing agent, the improvement wherein the textile material is impregnated with a mixture of the vat dye and an alkali metal bisulfite and the textile material impregnated with the vat dye and bisulfite is passed through an aqueous solution of a borohydride and an alkali metal hydroxide having a pH between about 9.5 and 13, said borohydride being selected from the group consisting of alkali metal borohydrides and quaternary ammonium borohydrides.

2. The method as claimed by claim 1 wherein the borohydride is an alkali metal borohydride.

3. The method as claimed by claim 1 wherein the borohydride is a water soluble quaternary ammonium borohydride.

4. The method as claimed by claim 1 wherein the alkali metal bisulfite is sodium bisulfite.

5. The method as claimed by claim 2 wherein the alkali metal borohydride is sodium borohydride.

6. The method as claimed by claim 4 wherein the borohydride is sodium borohydride.

References Cited in the file of this patent UNITED STATES PATENTS 2,745,788 Frohnsdorif May 15, 1956 2,991,152 Goerrig et al. July 4, 1961 FOREIGN PATENTS 1,036,228 Germany Aug. 14, 1958 OTHER REFERENCES Vickerstaif, The Physical Chemistry of Dyeing, pages 280-283, pub. by Interscience Pub. Inc., N.Y.C., 1954. 

1. IN A METHOD FOR CONTINUOUSLY DYEING TEXTILE MATERIALS WITH VAT DYES WHICH INVOLVES PADDING THE TEXTILE MATERIAL WITH AN AQUEOUS DISPERSION OF THE VAT DYE AND PASSING THE DYE IMPREGNATED TEXTILE MATERIAL THROUGH AN AQUEOUS SOLUTION OF A VAT DYE REDUCING AGENT, THE IMPROVEMENT WHEREIN THE TEXTILE MATERIAL IS IMPREGNATED WITH A MIXTURE OF THE VAT DYE AND AN ALKALI METAL BISULFITE AND THE TEXTILE MATERIAL IMPREGNATED WITH THE VAT DYE AND BISULFITE IS PASSED THROUGH AN AQUEOUS HAVING A PH BETWEEN ABOUT 9.5 AND 13, SAID BOROHYDRIDE BEING SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL BOROHYDRIDES AND QUATERNARY AMMONIUM BOROHYDRIDES. 